Latency, in a general sense, is a measure of time delay experienced in a system. In a non-trivial computer network, for example, a typical packet of data will be forwarded from a source to a destination over many links and via numerous intermediate gateway devices. Each link introduces a delay into the path of the data packet, and each gateway device generally does not start forwarding the received packet until it has been completely received.
In such a network, the minimal latency is the sum of the latency of each link (except the final one), plus the forwarding latency of each gateway. In practice, this minimal latency is further augmented by queuing and processing delays at the gateways. Queuing delays occur, for example, when a gateway receives multiple packets from different sources heading towards the same destination. Since often only one packet can be transmitted at a time by the gateway, some of the received packets must queue for transmission, thereby incurring additional delay. Processing delays, on the other hand, are incurred while a gateway determines what to do with a newly received packet. The combination of link, gateway, queuing, and processing delays, among others, may produce a complex and variable network latency profile.
There are some known ways of reducing and simplifying network latency, such as caching and aging of data based on geographical location. For example, caching may involve storing commonly-accessed data in geographically-nearby storage to avoid undue latency, while aging of data may involve deleting data from the cache that is older than a certain age. These techniques may not only reduce latency on the delivery of data but also may ensure the latest available data.
In a cloud computing or other distributed architecture, for example, location independence of terminals, such as mobile devices, may enable the terminals to access data on the cloud regardless of the location of the terminals or the stored data. Thus, the mobile devices may be frequently moving while maintaining access to data on the cloud.